Growth arrest and cell death in the breast tumor cell in response to ionizing radiation and chemotherapeutic agents which induce DNA damage

Department of Pharmacology, Virginia Commonwealth University/Medical College of Virginia, Richmond 23298, USA.
Breast Cancer Research and Treatment (Impact Factor: 4.2). 09/2000; 62(3):223-35. DOI: 10.1023/A:1006414422919
Source: PubMed

ABSTRACT Breast tumor cells are relatively refractory to apoptosis in response to modalities which induce DNA damage such as ionizing radiation and the topoisomerase II inhibitor, adriamycin. Various factors which may modulate the apoptotic response to DNA damage include the p53 status of the cell, levels and activity of the Bax and Bcl-2 families of proteins, activation of NF-kappa B, relative levels of insulin like growth factor and insulin-like growth factor binding proteins, activation of MAP kinases and PI3/Akt kinases, (the absence of) ceramide generation and the CD95 (APO1/Fas) signaling pathway. Prolonged growth arrest associated with replicative senescence may represent an alternative and reciprocal response to DNA-damage induced apoptosis that is p53 and/or p21waf1/cip1 dependent while delayed apoptosis may occur in p53 mutant breast tumor cells which fail to maintain the growth-arrested state. Clearly, the absence of an immediate apoptotic response to DNA damage does not eliminate other avenues leading to cell death and loss of self-renewal capacity in the breast tumor cell. Nevertheless, prolonged growth arrest (even if ultimately succeeded by apoptotic or necrotic cell death) could provide an opportunity for subpopulations of breast tumor cells to recover proliferative capacity and to develop resistance to subsequent clinical intervention.

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    • "On the other hand, there is proof that chemotherapy as ―induction therapy before radiotherapy‖ has no significant additive anti-tumor effects (Koukourakis et al., 1999). Breast tumors tend to resist and reoccur after the aforementioned treatments (Gewirtz, 2000). The exact nature and mechanisms of radiation responses of chemoresistant tumor cells remain obscure. "
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